Methods of performance analysis
You can use two methods for performance analysis:
measuring a system under full production load (full-load measurement),
to get all information that is measurable only under high system-loading,
and measuring single-application transactions (single-transaction measurement),
during which the system must not carry out any other activities.
Because a system can have various problems, it is not possible to recommend which option to use to investigate the behavior of a system. When in doubt about the extent of a problem, always use both methods.
Rapid performance degradation often occurs after a threshold is exceeded and the system approaches its ultimate load. You can see various indications only when the system is fully loaded (for example, paging, short-on-storage condition in CICS®, and so on), and you should usually plan for a full-load measurement.
The IBM® Redbooks® publication ABC's of z/OS® System Programming, Volume 11 contains further information about performance analysis methods.